CODEWITHSUNDEEP
c++sortingstlvector
HighLife
HighLife

Reputation: 4344

stl sort comparison class function

I'd like to use stl sort with a class comparison function greater that uses infoVec1 and infoVec2 but I'm getting a compile error:

Here is the class header

class Compare{
    Compare();
    std::vector< std::vector<std::string> >& infoVec1;
    std::vector< std::vector<std::string> >& infoVec2;


    public:

    bool greater(int one, int two);

    Compare(std::vector< std::vector<std::string> >& info1,
    std::vector< std::vector<std::string> >& info2);
};

I've initialized Compare in main like so:

Compare C = Compare(info1, info2);

And I'm trying to use great in main like:

sort(vec.begin(), vec.end(), C.greater);

And I'm getting this error:

main.cpp:266: error: no matching function for call to ‘sort(__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, <unresolved overloaded function type>)’
/usr/include/c++/4.2.1/bits/stl_algo.h:2852: note: candidates are: void std::sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, _Compare = bool (Compare::*)(int, int)]
make: *** [main.o] Error 1

How could I fix this class so that greater will work with stl sort?

Upvotes: 0

Views: 1531

Answers (1)

Loki Astari
Loki Astari

Reputation: 264411

Its easier to change the greater() method into operator()().

class Compare{
    Compare();
    std::vector< std::vector<std::string> >& infoVec1;
    std::vector< std::vector<std::string> >& infoVec2;


    public:

    bool operator()(int one, int two) const;  // this is used automatically.

    Compare(std::vector< std::vector<std::string> >& info1,
    std::vector< std::vector<std::string> >& info2);
};

Upvotes: 1

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